The biggest problem I see with this discussion is that we are back to square one in terms of how people perceive indie artist's means to generate revenue: selling music. IMO strictly selling music (or relying on streaming revenue) isn't what indie artists should be focusing on because they won't likely make much money even through the Itunes single market (which IMO is even worse for artists for multiple reasons, not to mention that it doesn't have the social/viral music discovery aspect that this new facebook music integration allows).
Don't forget about Mike Masnick's CwF + RtB = $$$ formula. Plenty of indie artists are connecting with fans and giving them a reasons to buy directly, which in turn appears to be a sustainable business model. Indie artists should also be looking at other revenue streams like selling merch, touring, and licensing/publishing monies.
Spotify is certainly no saving grace for all musicians. In fact, I think the real problem lies in the popular idea that it would some how allow musicians to make money selling music again. This unfortunately, but realistically, just isn't the case for most of us.

Facebook has forever shied away from music. The best it previously offered was limited integration with Root Music and Reverb Nation to host a pretty drab music tab. The people at Facebook seemed very aware that, while music essentially built Myspace, it was also the very thing that killed it....